Variable valve timing control apparatus with supplementary oil pump

ABSTRACT

A variable valve timing control apparatus includes: a relative rotational phase adjusting mechanism capable of adjusting a relative rotational phase between a drive-side rotational member and a driven-side rotational member between the most advanced angle phase and the most retarded angle phase; and a lock mechanism capable of locking the relative rotational phase at an intermediate phase between the most advanced angle phase and the most retarded angle phase; a first pump operated by a driving force of an engine; and an electrically driven second pump operated as an electrically driven pump. Hydraulic fluid is supplied from at least one of the first pump and the second pump, and the second pump is capable of operating even if the first pump is inoperative when the engine is not running.

TECHNICAL FILED

This invention generally relates to a variable valve timing control apparatus which controls opening and closing timings of one of, or both of, an intake valve and an exhaust valve, in response to running conditions of an engine mounted for example on a vehicle.

BACKGROUND ART

This type of variable valve timing control apparatus is mainly configured with a variable valve timing control unit and a relative rotational phase adjusting mechanism. The variable valve timing control unit incorporates, therein, a drive-side rotational member, which rotates in synchronization with a crankshaft; a driven-side rotational member, which is positioned coaxially with the drive-side rotational member and rotates integrally with a camshaft; at least one fluid pressure chamber defined in at least one of the drive-side rotational member and the driven-side rotational member; at least one vane dividing the fluid pressure chamber into an advanced angle chamber and a retarded angle chamber; and a relative rotational phase adjusting mechanism capable of changing a position of the at least one vane relative to the fluid pressure chamber by supplying, or draining, hydraulic fluid to or from at least one of the advanced angle chamber and the retarded angle chamber. The relative rotational phase adjusting mechanism is capable of adjusting a relative rotational phase between the drive-side rotational member and the driven-side rotational member between the most advanced angle phase, in which a volume of the advanced angle chamber reaches the maximum, and the most retarded angle phase, in which a volume of the retarded angle chamber reaches the maximum.

Further, in order to have the best condition for an engine start-up, a lock mechanism is provided for the purpose of locking the relative rotational phase between the drive-side rotational member and the driven-side rotational member at an intermediate phase between the most advanced angle phase and the most retarded angle phase. With this lock mechanism, a locked condition is established, for example by biasing, by a spring, a lock body provided to the drive-side rotational member towards the driven-side rotational member, and by inserting the lock body into lock oil chamber formed in the driven-side rotational member, preventing a relative rotation. This locked condition is released, for example by applying oil pressure to the lock oil chamber to retract the lock body towards the drive-side rotational member.

Conventionally, a variable valve timing control device has been provided with a mechanical pump, which is operated by a driving force from an engine, a mechanical pump which supplies hydraulic fluid employed for adjusting a relative rotational phase and lock oil employed for a lock operation by the lock mechanism. This type of variable valve timing control apparatus for an internal combustion engine is disclosed in JP2001-227308A (FIG. 6).

However, according to the above-described apparatus, supply of hydraulic fluid and lock oil depends on a so-called engine pump. In such a case, it is not possible to control opening and closing timings of valves when the engine is not running. Further, for example when an engine is started up, there is a valve timing suitable for an engine start-up, while there is a different valve timing suitable for a normal engine operation following the engine start-up. In order to establish the valve timing suitable for an engine start-up, a relative rotational phase between a driven-side rotational member and a drive-side rotational member is fixed (locked) at an initial phase by operating the lock mechanism. A lock condition of the relative rotational phase includes an engine stop lock performed immediately prior to an engine stop, and an engine start-up lock performed at a time of an engine start-up.

In the case of the engine stop lock, the relative rotational phase needs to be changed when an oil pressure level is declining immediately before an engine stop. Therefore, there is no guarantee that a reliable lock condition can be achieved.

In contrast, in the case of the engine start-up lock, the relative rotational phase is changed after turning on an ignition switch, i.e., when an oil pressure is unstable during an engine start-up. Therefore, the engine start-up could possibly be delayed by the time required for an engine start-up lock, and moreover, it is also possible that a reliable lock may not be achieved.

Further, a lock phase, at which the lock mechanism is operated and the relative rotational phase is fixed, is a phase or a valve timing which enables a good engine start-up when the engine has stopped running for a relatively long time and the engine temperature is low. At the lock phase, it is possible to assure a stable intake of air to the engine and sufficient level of actual compression ratio for stable combustion. Here, if the engine is stopped and is started again in a relatively short period of time at the lock phase set by the lock mechanism, cranking of the engine would require more work than required for the actual compression ratio necessary for stable combustion, thus requiring higher input voltage to a motor for cranking possibly with increased vibration of the motor.

The present invention has been made in view of the above circumstances, and provides a variable valve timing control apparatus which enables a good and smooth engine start-up operation.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, a variable valve timing control apparatus includes: a drive-side rotational member rotatable in synchronization with a crankshaft; a driven-side rotational member positioned coaxially with the drive-side rotational member and being rotatable integrally with a camshaft; at least one fluid pressure chamber defined at least one of the drive-side rotational member and the driven-side rotational member; at least one vane diving the fluid pressure chamber into an advanced angle chamber and a retarded angle chamber; a relative rotational phase adjusting mechanism capable of changing a position of the at least one vane relative to the fluid pressure chamber by supplying hydraulic fluid to or draining hydraulic fluid from at least one of the advanced angle chamber and the retarded angle chamber, the relative rotational phase adjusting mechanism being capable of adjusting a relative rotational phase between the drive-side rotational member and the driven-side rotational member between the most advanced angle phase, in which a volume of the advanced angle chamber reaches maximum, and the most retarded angle phase, in which a volume of the retarded angle chamber reaches maximum; a lock mechanism capable of locking the relative rotational phase at an intermediate phase between the most advanced angle phase and the most retarded angle phase; a first pump operated by a driving force of an engine; and an electrically driven second pump. Hydraulic fluid is supplied from at least one of the first pump and the second pump, and the second pump is capable of operating when the engine is stopped (i.e. when the engine is not running).

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:

FIG. 1 is a block view illustrating a variable valve timing control apparatus according to a first embodiment of the present invention;

FIG. 2 is a cross sectional view of the variable valve timing control apparatus illustrated in FIG. 1;

FIG. 3 is a cross sectional view illustrating a lock released condition in which a relative rotational phase control is achieved;

FIG. 4 is a cross sectional view illustrating a locked condition by a lock mechanism;

FIG. 5 is a cross sectional view illustrating the variable valve timing unit in which the most retarded angle phase is established;

FIG. 6 is an operation diagram of a control valve;

FIG. 7 is a flowchart for explaining an engine stop control according to the first embodiment of the present invention;

FIG. 8 is a flowchart for explaining an engine stop control according to a second embodiment of the present invention;

FIG. 9 is a flowchart for explaining an engine start-up control;

FIG. 10 is another example of the variable valve timing apparatus provided with another control valve in terms of a relative rotational phase control and a lock control;

FIG. 11 is a block view illustrating a variable valve timing control apparatus according to the second embodiment of the present invention;

FIG. 12 is a block view illustrating a variable valve timing control apparatus according to a third embodiment of the present invention;

FIG. 13 is a block view illustrating a variable valve timing control apparatus according to a fourth embodiment of the present invention;

FIG. 14 is a flowchart for explaining an engine stop control according to the third embodiment of the present invention; and

FIG. 15 is a flowchart for explaining an engine stop operation predicting control according to a fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinbelow in detail with reference to the accompanying drawings.

According to a first embodiment of the present invention, as is illustrated in FIG. 1, variable valve timing control units 100 are provided to an intake camshaft 3 a and an exhaust camshaft 3 b, respectively.

1. An Entire Structure of a Variable Valve Timing Control Apparatus

As is illustrated in FIG. 1, a variable valve timing control apparatus 1 includes an intake camshaft rotational angle sensor 9 a for detecting a rotational speed of the intake camshaft 3 a for opening and closing an intake valve Ei of an engine E, an exhaust camshaft rotational angle sensor 9 b for detecting a rotational speed of the exhaust camshaft 3 b for opening and closing an exhaust valve Eo, a crankshaft rotational angle sensor (an engine rotational speed sensor) 9 c for detecting a rotational speed of a crankshaft 12, a throttle valve 14 located in an intake passage 13 and capable of controlling an amount of intake air, an electronic control throttle 16, which is configured with a throttle valve opening degree sensor 9 d for detecting an opening degree of the throttle valve 14 and a throttle motor 15 for operating the throttle valve 14, and an electronic control unit (ECU) 9 for controlling the electronic control throttle 16 among other components.

As is illustrated in FIG. 1, the ECU 9 incorporates, therein, modules that are characteristic to the first embodiment of the present invention, such as a relative rotational phase controlling module (i.e., a relative rotational phase controlling means) 90, an engine start-up predicting module (i.e., an engine start-up predicting means, E-start predicting module) 91, an engine start-up controlling module (i.e., an engine start-up controlling means) 92, an engine stop predicting module (i.e., an engine stop predicting means, E-stop predicting module) 93, and an engine stop controlling module (i.e., an engine stop controlling means) 94. The ECU 9 serves as a control unit for controlling the variable valve timing control apparatus 1. The ECU 9 has, among other necessary components, one or more memory units for storing predetermined programs and data, one or more central processing unit(s) (CPU), and input/output interfaces. Each of the modules is a part of software that runs in the ECU 9 together with any associated hardware required to carry out the function(s) and algorism associated with the module, which will be described below. The associated hardware may be shared or not shared by different modules. While a separate subroutine may be associated with each module, a group of interdependent subroutines may configure a group of modules. It is also possible to have one main program that has all the algorisms for performing all the functions of the modules.

Relative rotational phase control implemented by the ECU 9 is described below in terms of the variable valve control unit 100 at an exhaust side. The ECU 9 receives signals from the crankshaft rotational angle sensor 9 c and the exhaust camshaft rotational angle sensor 9 b. The relative rotational phase controlling module 90 obtains, on the basis of a difference between the received signals, a relative rotational phase, or a phase difference of the exhaust valve Eo relative to the angular position of the crankshaft 12. The phase difference substantially corresponds to an actual timing for opening and closing the exhaust valve Eo.

On the other hand, in a memory module (a memory means, a memory) 95 of the ECU 9, relative rotational phases optimized for respective driving conditions of the engine E have been stored. The relative rotational phase controlling module 90 is capable of identifying the optimum relative rotational phase in response to an actually detected engine driving condition, for example an engine rotational speed and a temperature of cooling water. This relative rotational phase controlling module 90 then generates and outputs a control command by which an actual relative rotational phase is controlled at the optimum relative rotational phase suitable for the actual driving condition of the engine E.

As is illustrated in FIG. 2, the control command from the ECU 9 is transmitted to a control valve 76 so as to adjust the position of its spool appropriately. This control valve 76 is supplied with oil pressure from a first pump 70 a or a second pump 70 b, which is characteristic to the first embodiment of the present invention to effect the relative rotational phase control, the engine start-up control, and the engine stop control. The first pump 70 a is a mechanical pump operated by a driving force from the engine E, while the second pump 70 b is an electrically driven pump that is connected to a motor and is supplied with electric power from an electric system. The first pump 70 a is operated while the engine E is running, primarily for implementing the relative rotational phase control. The second pump 70 b is operated primarily for the above-described engine start-up control or engine stop control.

According to the first embodiment of the present invention, as is illustrated in FIG. 1, the first pump 70 a and the second pump 70 b are arranged in parallel with each other. With this arrangement, since both the first pump 70 a and the second pump 70 b directly communicate with an oil pan 75, even when the engine E is stopped, it is possible to supply oil to other portions which still remain at a high temperature, for example bearings of a supercharger (not illustrated) by operating the second pump 70 b after the engine E has stopped running. Therefore, oil degradation can be effectively prevented.

The ECU 9 is further capable of controlling an opening degree of the throttle valve 14, on the basis of an engine rotational speed, which is calculated from signals from the crankshaft rotational angle sensor 9 c, signals from a timer provided to the ECU 9, and signals from the throttle valve opening degree sensor 9 d. Therefore, the ECU 9 can appropriately control the engine, for example, at an engine start-up.

The ECU 9 further receives information on the position (i.e. on or off position) of an ignition key 9 e (IG key), information on a door opening operation from a door opening and closing sensor 9 f, information on an engine oil temperature from an oil temperature sensor 9 g, information on a temperature of an engine cooling water from a cooling water temperature sensor 9 h, and information on an outside air temperature from an air temperature sensor 9 i.

2. Variable Valve Timing Control Unit 100

As is illustrated in FIG. 2, the variable valve timing control unit 100, for example for the exhaust side, is mainly configured with an external rotor 2 (a drive-side rotational member), which rotates in synchronization with the crankshaft 12 of the engine E of a vehicle, and an internal rotor 1 (a driven-side rotational member), which is located coaxially with the external rotor 2 and rotates integrally with the camshaft 3.

The internal rotor 1 is integrally attached to the tip end of respective camshaft 3 a or 3 b, which is supported by a cylinder head. The external rotor 2 is mounted outside of the internal rotor 1 so as to be rotatable relative to the internal rotor 1 within a predetermined relative rotational phase, and is mainly configured with a front plate 22, a rear plate 23 and a timing sprocket 20 that is integrally provided to an external periphery of the external rotor 2.

A power transmission member 24 such as a timing chain or a timing belt is provided between the timing sprocket 20 and a gear attached to the crankshaft 12 of the engine E.

According to the variable valve timing control unit 100 according to the first embodiment of the present invention, when the crankshaft 12 of the engine E is rotated, rotational force is transmitted to the timing sprocket 20 via the power transmission member 24, and the external rotor 2 with the timing sprocket 20 rotates in the rotational direction S shown in FIG. 3. Further, the internal rotor 1 rotates in the rotational direction S to rotate the camshaft 3. A cam fixedly mounted on the camshaft 3 pushes down the intake valve Ei or the exhaust valve Eo to open the valve.

(Fluid Pressure Chamber)

As is illustrated in FIG. 3, a plurality of protrusions 4, serving as shoes projected radially inwardly from an inner periphery of the external rotor 2, are arranged at the external rotor 2 with intervals from each other along the rotational direction. A fluid pressure chamber 40, which is defined between the internal rotor 1 and the external rotor 2, is formed between the adjacent protrusions 4 of the external rotor 2. For example, four fluid pressure chambers 40 are formed according to the first embodiment of the present invention. The fluid pressure chamber 40 may be formed in at least one of the external rotor 2 and the internal rotor 1.

A vane groove 41 is formed on an external peripheral portion of the internal rotor 1 facing each fluid pressure chamber 40. A vane 5 for dividing the fluid pressure chamber 40 into an advanced angle chamber 43 and a retarded angle chamber 42 in a relative rotational direction (i.e., in the direction of arrows S1, S2 of FIG. 3) is slidably located in the vane groove 41 in a radial direction.

The advanced angle chamber 43 of the fluid pressure chamber 40 communicates with an advanced angle passage 11 formed at the internal rotor 1, while the retarded angle chamber 42 communicates with a retarded angle passage 10. The advanced angle passage 11, and the retarded angle passage 10, for each fluid pressure chamber 40 is connected to an hydraulic circuit 7.

(Hydraulic Circuit)

As is illustrated in FIGS. 2 and 3, the hydraulic circuit 7 supplies and drains, via the advanced angle passage 11 and the retarded angle passage 10, engine oil as hydraulic fluid for one of, or both of, the advanced angle chamber 43 and the retarded angle chamber 42. Thus, the hydraulic circuit 7 is capable of acting as a relative rotational phase adjusting mechanism, whereby a relative position of the vane 5 in each fluid pressure chamber 40 can be altered, and a relative rotational phase between the internal rotor 1 and the external rotor 2 (hereinafter, referred to as a relative rotational phase) can be adjusted between the most advanced angle phase and the most retarded angle phase. The most advanced angle phase corresponds to a relative rotational phase between the rotors 1 and 2 where the volume of the advanced angle chamber 43 reaches maximum, while the most retarded angle phase corresponds to a relative rotational phase between the rotors 1 and 2 where the volume of the retarded angle chamber 42 reaches maximum. FIG. 5 illustrates the most retarded angle phase in the variable valve timing control unit 100.

In more detail, as is illustrated in FIGS. 1 and 2, the hydraulic circuit 7 incorporates the first pump 70 a, which is operated by a driving force from the engine E and is capable of supplying, to the control valve 76, engine oil as hydraulic fluid or locking oil described later, and the electrically driven second pump 70 b. The second pump 70 b is switched on and off in response to a control command from the ECU 9. Further, the control valve 76 is provided at a predetermined portion of the hydraulic circuit 7, for example at a position downstream of the pump 70 and upstream of the advanced angle chamber 43, the retarded angle chamber 42 and lock oil chamber 62. According to the first embodiment of the present invention, the control valve 76 is for example a solenoid-type valve in which a position of a spool can be changed in response to control of an amount of electricity supplied from the ECU 9, and engine oil can be supplied and drained through its plurality of ports. The hydraulic circuit 7 further incorporates the oil pan 75 for storing engine oil therein. The advanced angle passage 11, and the retarded angle passage 10, of each fluid pressure chamber 40 are connected to predetermined ports of the control valve 76.

(Biasing Mechanism)

As is illustrated in FIG. 2, a torsion spring 8, which serves as a biasing mechanism capable of biasing the relative rotational phase between the rotors 1 and 2 towards the advanced angle side, is provided between the internal rotor 1 and the external rotor 2. As is illustrated in FIG. 3, this torsion spring 8 biases the external rotor 2 relative to the internal rotor 1 in the direction denoted with S1. This torsion spring 8 enables a start-up lock which is characteristic of the present invention.

(Lock Mechanism and Lock Oil Chamber)

A lock mechanism 6 is provided between the internal rotor 1 and the external rotor 2. The lock mechanism 6 is capable of locking or preventing a relative rotation between the internal rotor 1 and the external rotor 2 when the relative rotational phase between the rotors 1 and 2 is at a predetermined intermediate phase (lock phase) defined between the most advanced angle phase and the most retarded angle phase. According to the first embodiment of the present invention, this intermediate phase corresponds to the first start-up phase.

As is illustrated in FIG. 3, the lock mechanism 6 is configured with a lock portion 6A for a retarded angle, a lock portion 6B for an advanced angle, both of which are provided to the external rotor 2, and a recessed lock oil chamber 62 provided in an external peripheral portion of the internal rotor 1.

The lock portion 6A for a retarded angle and the lock portion 6B for an advanced angle each includes a lock body 60 provided in the external rotor 2 to be freely slidable in a radial direction, and a spring 61 for biasing the lock body 60 in a radially inward direction. The lock body 60 may be shaped in a plate configuration, pin configuration and other configurations.

The lock portion 6A for a retarded angle prevents, by inserting the lock body 60 into the lock oil chamber 62, a relative rotation of the internal rotor 1 relative to the external rotor 2 in the retarded angle direction (in the direction denoted with S1 in FIG. 3) from the lock phase. The lock portion 6B for an advanced angle prevents, by inserting its lock body 60 into the lock oil chamber 62, a relative rotation of the internal rotor 1 relative to the external rotor 2 in the advanced angle direction (in the direction denoted with S2 in FIG. 3) from the lock phase. That is, in case one of the lock portion 6A for a retarded angle and the lock portion 6B for an advanced angle is being projected into the lock oil chamber 62, a phase change to the side of the one of the retarded angle side and the advanced angle side is prevented while allowing a phase change to the opposite side.

As is illustrated in FIG. 4, by inserting the lock bodies 60, 60 for the lock portion 6A for a retarded angle and for the lock portion 6B for an advanced angle into the lock oil chamber 62, the so-called locked condition is established in which a relative rotational phase between the rotors 1 and 2 is locked at the predetermined intermediate phase (the lock phase) defined between the most advanced angle phase and the most retarded angle phase. The lock phase is set to be a phase at which the opening and closing timings, of the intake valve Ei and the exhaust valve Eo, are appropriate for obtaining smooth start-up of the engine E.

The lock oil chamber 62 communicates with a lock oil passage 63 formed in the internal rotor 1, and the lock oil passage 63 is connected to a predetermined port of the control valve 76 of the hydraulic circuit 7. That is, the hydraulic circuit 7 is configured to supply, or drain, engine oil as lock oil from or to the lock oil chamber 62. When lock oil is supplied from the control valve 76 to the lock oil chamber 62, as is illustrated in FIG. 3, the lock bodies 60 are retracted to the side of the external rotor 2, wherein the rotors 1 and 2 are released from the locked condition thereby allowing a relative rotation. This release of the locked condition is effected when, for example, a variable valve control, such as an advanced angle control and a retarded angle control, is commenced after a smooth engine start-up has been executed in the intermediate locked condition.

(Oil Pressure Passage)

As is illustrated in FIGS. 1 and 6, a spool of the control valve 76 of the hydraulic circuit 7 is selectively positioned from a position W1 to a position W5, in proportion to or as a function of an amount of electricity supplied from the ECU 9 to supply, drain, or stop the flow of engine oil (either as hydraulic fluid or lock oil) to or from the advanced angle chamber 43, the retarded angle chamber 42, and the lock oil chamber 62.

In more detail, when the spool of the control valve 76 is located at the position W1, a drain operation is performed wherein lock oil in the lock oil chamber 62 as well as hydraulic fluid in the advanced angle chamber 43 and the retarded angle chamber 42 are drained to the oil pan 75.

When the spool of the control valve 76 is located at the position W2 (either W2 a or W2 b), either one of the advanced angle chamber 43 and the retarded angle chamber 42 is supplied with hydraulic fluid so that the vane 5 is shifted towards the advanced angle side or the retarded angle side while lock oil in the lock oil chamber 62 is drained to the oil pan 75. In this case, as long as the relative rotational phase has not reached the intermediate phase (i.e. the lock phase), the relative rotational phase is changed either to the advanced angle side or to the retarded angle side. The locked condition is established when the relative rotational phase reaches the intermediate phase.

When the spool of the control valve 76 is located at the position W3, an advanced angle operation is implemented wherein the relative rotation between the rotors 1 and 2 is released from the locked condition by supplying lock oil to the lock oil chamber 62, and hydraulic fluid is supplied to the advanced angle chamber 43 while draining hydraulic fluid from the retarded angle chamber 42, whereby the relative rotational phase between the rotors 1 and 2 is shifted in the advanced angle direction denoted by S2. When the spool of the control valve 76 is located at the position W4, a phase maintaining operation is implemented wherein the relative rotation between the rotors 1 and 2 is released from the locked condition, and a supply of hydraulic fluid to the advanced angle chamber 43 and the retarded angle chamber 42 is halted, wherein the relative rotational phase between the rotors 1 and 2 is maintained as it is at that time.

When the spool of the control valve 76 is located at a position W5, a retarded angle operation is implemented wherein the relative rotation between the rotors 1 and 2 is released from the locked condition, and the retarded angle chamber 42 is supplied with hydraulic fluid while draining hydraulic fluid from the advanced angle chamber 43, whereby the relative rotational phase between the rotors 1 and 2 is shifted in the retarded angle direction denoted by S1. The operation, and the structure, of the control valve 76 is not limited to the above, and any modifications can be applied.

3. Structure Characteristic to the Present Invention

The structure of the variable valve timing control apparatus 1 according to the first embodiment of the present invention was described above. Next, described below are controls implemented by the variable valve timing control apparatus 1.

The variable valve timing control apparatus 1 mainly implements the following three controls: 1) a relative rotational phase control while the engine E is running in normal operation; 2) an engine start-up control when the engine E is started up; and 3) an engine stop control during the engine stop operation. According to the first embodiment of the present invention, while the relative rotational phase control is being implemented, the first pump 70 a is operated, and at a time of the engine start-up control or the engine stop control, the second pump 70 b is operated so as to implement an engine start-up lock or an engine stop lock. The relative rotational phase control is implemented by the relative rotational phase controlling module 90, the start-up control is implemented by the engine start-up controlling module 92, and the engine stop control is implemented by the engine stop controlling module 94. The memory module 95 stores, therein, second start-up phases, which are appropriate phases for starting up the engine E and are determined based upon at least one of an engine oil temperature, a water temperature, an intake air temperature, and an outside air temperature, as well as information required for the relative rotational phase control. Therefore, by setting the relative rotational phase at the second start-up phase appropriate for an engine start-up, it is possible to achieve a good engine start up. For example, by memorizing engine oil temperatures, water temperatures, outside air temperatures and so on in a table as a parameter, it is possible to set a relative rotational phase experientially appropriate.

(1) Relative Rotational Phase Control

The relative rotational phase control is carried out in such a manner that the relative rotational phase between the rotors 1 and 2 is suitable for a operating condition of the engine E. While the relative rotational phase control is being carried out, the lock mechanism 6 is not in operation. That is, the advanced angle control, the retarded angle control, and the phase maintaining control are implemented with the lock oil chamber 62 supplied with lock oil and thus with the lock bodies 60 retracted from the lock chamber 62 as shown in FIG. 3.

Therefore, for the duration of the relative rotational phase control, the spool 76 a of the control valve 76 is controlled to be positioned within a range that includes the positions W3, W4 and W5 but that excludes the positions W1 and W2 as illustrated in FIG. 6. The relative rotational phase controlling module 90 of the ECU 9 obtains, on the basis of a relationship between a rotational angle of the crankshaft 12 and a rotational angle of the camshaft 3, the actual value of the relative rotational phase between the external rotor 2 and the internal rotor 1. At the same time, based on the operating condition (an engine rotational speed, a cooling water temperature and so on) of the engine E, the ECU 9 determines a target value of a relative rotational phase, which is suitable for the engine operating condition, from the values stored in the memory module 95. Based on the relationship between the value actually derived, and the target value, of the relative rotational phase, the ECU 9 generates and outputs a control command to the control valve 76. For example, this control command is outputted in the form of an electric current value, and this electric current value can be increased, maintained, and reduced, in accordance with the relationship between the actual value, and the target value, of the relative rotational phase.

(2) Start-Up Control and Stop Control

According to the first embodiment of the present invention, not only the first pump 70 a, which has been conventionally employed and supplies oil pressure using a driving force of the engine E, is provided, but also the electrically driven second pump 70 b is provided. Therefore, even when the engine E is not running (or halted), it is possible, by appropriately controlling an operation of the second pump 70 b, to implement the relative rotational phase control or to obtain the oil pressure required for carrying out a lock control. As a result, even when an engine stop lock is implemented in response to an engine halting, or even when the engine start-up lock is implemented in response to a start-up of the engine E, the second pump 70 b makes it possible to effect these controls with high reliability and precision, which was not achieved by a conventional variable valve timing control apparatus.

When the engine stop operation is implemented, preparations needed for an appropriate engine start-up are made on the basis of a signal representing this engine stop operation, e.g., an off operation of the ignition key 9 e. Also, when the engine is started again, regardless of completion of the preparations during the engine stop, likewise, the relevant parts are controlled in order to achieve an appropriate engine start-up.

Next, described below are an engine stop control and an engine start control that is carried out after the engine stop control, with reference to flowcharts illustrated in FIGS. 7, 8 and 9. In each flowchart, the module (means), which acts each step, is indicated on the left side thereof, and operating conditions, of the first pump 70 a and the second pump 70 b, which are characteristics of the present invention, are indicated on the right side thereof.

(2-1) Engine Stop Control

As described above, the engine stop control is implemented starting from the intermediate locked condition when the engine E is started again. Or, the engine stop control is implemented so as to establish the intermediate locked condition smoothly and easily when the engine E is stared again. This engine stop control involves the engine stop predicting module 93 and the engine stop controlling module 94.

According to the first embodiment of the present invention, there are two examples with regard to this engine stop control. FIG. 7 illustrates the first engine stop control, while FIG. 8 illustrates the second engine stop control. In these examples, the operation of the first pump 70 a is discontinued in response to the halting of the engine E. The subsequent operation for maintaining the oil pressure level is carried out by the second pump 70 b, wherein the engine stop control is performed in order to perform a predetermined intermediate lock.

The two examples differ in that the first example of the engine stop control concerns whether a relative rotational phase is at the intermediate lock phase, and whether a predetermined period of time has passed after turning the ignition key 9 e to its off position whereas the second example concerns the number of sweep operations described later is referred to as the basis for determining termination of the engine stop control. Each example is described in detail next.

(2-1-1) First Example of the Engine Stop Control

This engine stop control is implemented following the flowchart illustrated in FIG. 7.

Step 71

The engine stop-predicting module 93 determines whether the ignition key 9 e is turned to its off position. If the ignition key 9 e is not turned to the off position (i.e. No at step 71), the program proceeds to step 70 so as to perform the above-described relative rotational phase control. Since the engine E is still running, the first pump 70 a continues to operate. Further, the spool of the control valve 76 is located at one of the positions W3, W4 and W5 described above.

Step 72

If the ignition key 9 e is turned to the off position resulting in “Yes” in step 71, the program proceeds to step 72 to initiate the operation of the second pump 70 b on the basis of the control command from the engine stop controlling module 94.

Steps 73 and 74

At or about the same time, the ECU 9 outputs a control command to the control valve 76 to shift the spool of the control valve 76 from one of the positions W3, W4, and W5 to the position W2. That is, in order to operate the lock mechanism 6, the oil is drained from the lock oil chamber 62. This drain operation at step 73 is continued until an engine rotational speed drops down to zero. When the engine rotational speed reaches zero, oil supply by the first pump 70 a stops completely.

Step 75

When oil supply by the first pump 70 a is completely stopped, a sweep control is performed by oil pressure from the second pump 70 b. This sweep control is a control where an advanced angle operation is carried out over a predetermined period of time while the oil pressure in the lock oil chamber 62 is approximately zero. The spool of the control valve 76 is located at the position W2 a where the volume of the advanced angle chamber 43 is increased. Normally, in such circumstances, because the engine E has stopped after idling, the relative rotational phase is set at the most retarded angle phase. Therefore, by gradually moving the vane 5 towards the advanced angle side by this sweep control, it is possible to shift the relative rotational phase to the intermediate phase, where the locked condition can be established, by means of the oil pressure from the second pump 70 b. The program then proceeds from step 75 to step 76 during this advanced angle operation, or after performing this advanced angle operation over the predetermined period of time.

Step 76

The ECU 9 determines whether the relative rotational phase has reached the intermediate phase at which the locked condition can be established in step 76. If it has, and a positive answer yes is obtained at step 76, the program proceeds to step 78, wherein the engine stop control is terminated. In constant, If the intermediate phase has not been reached, and a negative answer no is obtained at step 76, the program proceeds to step 77.

Step 77

This decision step 77 is to set a limit to the maximum period of time for performing the engine stop control. The ECU 9 determines, on the basis of an elapsed time after turning the ignition key 9 a to its off position, whether the sweep control at step 75 should be repeated or the engine stop control at step 78 should be terminated. When the predetermined period of time has passed at step 77, the program proceeds to step 78 so as to terminate the engine stop control. On the other hand, when the predetermined period of time has not passed at step 77, the program returns to step 75 so as to further perform the advanced angle operation and to shift the relative rotational phase from the retarded angle side to the intermediate phase.

(2-1-2) Second Example of the Engine Stop Control

This engine stop control is implemented following the flowchart illustrated in FIG. 8.

The second example of the engine stop control differs from the first example in that the number of implementing the sweep control at steps 85 and 86 are limited; therefore, when the predetermined number of sweep controls is performed, the engine stop control is terminated.

Step 81

The engine stop predicting module 93 determines whether the ignition key 9 e is turned to the off position. If it is, and a negative answer no is obtained at step 81, the program proceeds to step 80 so as to perform the above-described relative rotational phase control. Since the engine E is still running, the first pump 70 a remains operative. Further, the spool of the control valve 76 is located at one of the positions W3, W4 and W5.

Step 82

If the ignition key 9 e was turned to the off position resulting in “Yes” at step 71, the program proceeds to step 72 to initiate the operation of the second pump 70 b on the basis of the control command from the engine stop controlling module 94.

Steps 83 and 84

At or about the same time, the ECU 9 outputs a control command to the control valve 76 to shift the spool of the control valve 76 from one of the positions W3, W4, and W5 to the position W2. That is, in order to operate the lock mechanism 6, the oil is drained from the lock oil chamber 62. This drain operation at step 73 is continued until an engine rotational speed drops down to zero. When the engine rotational speed reaches zero, oil supply by the first pump 70 a stops completely.

Steps 85 and 86

When oil supply by the first pump 70 a is completely stopped, a sweep control is performed by oil pressure from the second pump 70 b. This sweep control is a control where an advanced angle operation or the retarded angle operation is repeatedly carried out at a predetermined time interval while an oil pressure in the lock oil chamber 62 is approximately zero. That is, at step 85, a predetermined procedure is implemented each time step 85 is carried out. For example, when the program passes step 85 for the first time, the advanced angle operation is implemented for two seconds. When the program passes step 85 for the second time, the retarded angle operation is implemented for two seconds. When the program passes step 85 for the third time, the advanced angle operation is again implemented for two seconds. When the program passes step 85 for the fourth time, the retarded angle operation is again implemented for two seconds. The spool of the control valve 76 is located at the position W2 a for the advanced angle operation or at the position W2 b for the retarded angle operation. Here, the period of time for performing a single retarded or advanced angle operation corresponds to a time required for the relative rotational phase to move past the intermediate lock phase. As described above, during one of the sweep operations, the relative rotational phase reaches the intermediate phase, wherein the locked condition is established appropriately. The number of times for implementing the sweep operations is determined at step 86.

As a result, by performing the predetermined number of sweep operations, it is possible to establish the locked condition appropriately. Further, this algorism allows the sweep operation to discontinue even when the locked condition is not established for some reason, and at step 87, the engine stop control is terminated.

(2-2) Engine Start-Up Control

This engine start-up control is implemented to achieve an appropriate engine start-up responsive to the condition of the starting engine E regardless of the condition of the engine at the time of the previous engine stop operation. This engine start-up control involves the engine start-up predicting module 91 and the engine start-up controlling module 92.

In recent vehicles, when a door opening operation is detected after the engine E has been inactive for a relatively long time, the vehicle controller expects an engine start-up. Likewise, in a keyless entry system, when a user with a vehicle key approaches a vehicle, the system recognizes this approach, and prepares to release the door from the locked condition. These recognition systems can understand that an engine start-up is to be expected soon. It is also advantageous for a variable valve timing control apparatus to be able to prepare for an engine start-up for the purpose of appropriately starting an engine. Therefore, according to the first embodiment of the present invention, the engine start-up predicting module 91 recognizes, for example on the basis of a door opening operation, that an engine start-up is soon performed even when the engine is not yet started.

Here, this engine start-up control is performed by operating the second pump. In this case, preparations for starting the engine E is made, for example by setting the relative rotational phase between the drive-side rotational member and the driven-side rotational member suitable for an engine start-up. Accordingly, by performing this engine start-up control prior to an actual engine start-up, or at or about the same time as the actual engine start up, it is possible to start up the engine E smoothly and appropriately.

The engine start-up control according to the first embodiment of the present invention is illustrated by the flowchart illustrated in FIG. 9. This engine start-up control is based on the premise that the engine E has not been started yet. Therefore, after the second pump 70 b has been operated to bring certain parts to speed, the engine E is started and the first pump 70 a starts to operate.

Further, according to this engine start-up control, a water temperature of the engine cooling water is monitored. The phase for the engine start-up may be selected between the intermediate phase (the locked phase) at which the lock mechanism 6 is operated, and a phase which is different from the intermediate phase depending on the water temperature.

The engine start-up lock phase is determined to be the phase at which an appropriate engine start-up can be performed when the temperature of the engine E remains relatively low. Therefore, when the temperature of the engine E is relatively high, it is not so good to perform an engine start-up at this engine start-up lock phase. In light of the foregoing, by setting the relative rotational phase at the second start-up phase, which is different from this engine start-up lock phase, it is possible to appropriately start the engine E even when the temperature of the engine E is still at a relatively high level. The second start-up phase is, for example, a phase at which an engine can be appropriately started even when the engine E is relatively warm.

In case the second start-up phase is set when the engine E is started, for example, after stopping the engine E and prior to starting the engine E, a sweep operation is implemented for adjusting the relative rotational phase to the most advanced angle phase side or the most retarded angle phase side. By operating the lock mechanism 6, even when the engine stop lock control is being implemented for fixing the relative rotational phase at the first start-up phase appropriate for an engine start-up, it is possible to set a relative rotational phase which is suitable for an actual engine operating condition when the engine is actually running, thereby achieving a good engine start-up.

Step 91

The engine start-up predicting module 91 determines the presence, or absence, of the possibility of the ignition key 9 e being turned to its on position. For example, when a signal representing a door opening operation is detected while the engine E is not running, the engine star-up predicting module 91 determines the presence of the possibility of the ignition key 9 e being turned to its on position. In other words, the engine start-up predicting module 91 predicts the soon-to-be-performed start-up of the engine E on the basis of the operation of the ignition key 9 e. The program then proceeds to step 92.

As described above, the engine start-up control is commenced when the engine start-up is predicted. Therefore, when a door opening operation is not detected at step 91, the program proceeds to step 90 so as to establish an engine start-up standby condition in which a door opening operation is waited and in which both the first pump 70 a and the second pump 70 b are not operated. Further, the spool of the control valve 76 is located at the position W1.

Step 92

The ECU 9 detects an engine water temperature in this step. The ECU 9 determines, on the basis of the engine water temperature, whether the engine E should be started at the intermediate phase or at a phase different from the intermediate phase. For example, when the temperature of the engine E has dropped down to a normal temperature, the engine can be started up at the intermediate phase. When the engine E is still warm because it has not been long since it stopped running, the engine can be started up at a different phase, for example a phase more toward the side of the retarded angle with respect to the intermediate phase (the lock phase).

Step 93

Here, the ECU 9 selects an appropriate control on the basis of the engine water temperature detected at step 92. When the engine water temperature is lower than 20 degrees, the program proceeds to step 93-1, wherein the intermediate locked condition is maintained. This intermediate locked condition is established during the engine stop control described above. Therefore, the algorism waits for an engine start-up (step 101) in such a state that the engine E can be started up smoothly when the engine E is at a relatively low temperature.

Step 93-2

When the engine water temperature is higher than 20 degrees at step 93, the program proceeds to step 93-2, wherein the second pump 70 b is operated.

Step 94

The ECU 9 calculates, on the basis of the detected engine water temperature, a relative rotational phase which is optimal for the engine start-up. As described above, the optimal relative rotational phase can be obtained by selecting a value from the relative rotational phase values stored in the memory module 95, or by interpolating discrete values of the relative rotational phase. The calculated relative rotational phase will be a phase different from the intermediate lock phase, and is recognized as a target phase employed at step 99.

Step 95

Lock oil is supplied to the lock oil chamber 62 to make it possible for implementing the retarded angle control wherein the relative rotational phase at step 96 is controlled to the most retarded angle phase. The spool of the control valve 76 is located at one of the positions W3, W4 and W5 where the locked condition is released. Accordingly, the lock bodies 60 are released from the lock oil chamber 62, wherein the relative rotational phase control can be implemented.

Step 96

The relative rotational phase is controlled to the most retarded angle phase in this step. The spool of the control valve 76 is located at the position W5 for increasing the volume of the retarded angle chamber 42.

Step 97

The ECU 9 implements initial phase learning. In this initial phase learning, the relative rotational phase in step 96 is recognized as the most retarded angle phase. For example, when the most retarded angle phase is recognized as zero degree, and the most advanced angle phase is recognized as 60 degrees, the relative rotational phase reached at step 96 is updated as a zero phase. Therefore, it is possible to guarantee a zero point of the relative rotational phase, which is determined independently for each variable valve timing control unit.

Steps 98 and 99

As described above, when the engine water temperature is relatively high, it is preferable to start up the engine E with the relative phase on the side of the retarded angle with respect to the intermediate lock phase, and an appropriate phase is obtained at step 94. Therefore, in step 98, the ECU 9 implements, over a predetermined period of time, a relative rotational phase control wherein the relative rotational phase is shifted to the advanced angle side. In step 99, the ECU 9 determines whether the relative rotational phase reached the target phase. In this case, the spool of the control valve 76 is located at the position W3 for the advanced angle operation. Here, the actual relative rotational phase is controlled to remain within plus or minus 10 degrees relative to the target phase with respect to the crank shaft angle.

Step 100

The ECU 9 implements a relative rotational phase maintaining control for maintaining the relative rotational phase reached in steps 98 and 99.

Step 101

The ECU 9 implements the engine start-up standby control by which a start-up of the engine E is waited. As described above, the engine start-up control is completed. According to the first embodiment of the present invention, on the basis of the engine water temperature, the engine start-up is waited with the relative phase between the intermediate lock phase and a phase being different from the intermediate lock phase. Therefore, prior to operating the ignition key 9 e, the actual relative rotational phase can be shifted to a phase which is suitable for an actual engine driving condition, and the engine E can then be started up, making it possible to have a smooth and accurate engine start up. As described above, according to the first embodiment of the present invention, as illustrated in FIG. 2, both the relative rotational phase control and the lock control are performed by means of a single control valve. As is illustrated in FIG. 10, a control valve 760 (for example, a normally used three way valve) for a relative rotational phase control and another control valve 761 (for example, a normally used three way valve) for a lock control may be provided. This may make it less likely to have an accidental lock during the relative rotational phase control.

SECOND EMBODIMENT

As is illustrated in FIG. 11, in a variable valve timing control apparatus 1 according to the second embodiment of the present invention, the first pump 70 a is arranged in series with the second pump 70 b, while other configuration thereof is substantially identical to the first embodiment.

According to the second embodiment of the present invention, the second pump 70 b is arranged in series with and on the downstream side of the first pump 70 a. An oil reservoir 71 is provided between the first pump 70 a and the second pump 70 b. This oil reservoir 71 can store an amount of oil drawn from the oil pan 75 by the first pump 70 a. When the first pump 70 a is operating, oil is supplied to each portion of the engine E via a main oil passage 72 from the oil reservoir 71, and is supplied to the variable valve timing control unit 100 via the control valve 76. When the first pump 70 a is inoperative in response to the halt of the engine E, the second pump 70 b draws oil accumulated in the oil reservoir 71 and supplies the oil to the variable valve timing control unit 100. Here, a volume of the oil reservoir 71 can be determined to be the volume required for the variable valve timing control unit 100 to implement the engine start-up control or the engine stop control. For example, if the vane 5 is shifted from the most advanced angle side to the most retarded angle side with a volume change of about 30 cc, it is preferable that the oil reservoir 71 has a volume of approximately 60 cc which substantially corresponds to an amount required for the variable valve timing control unit 100 to cause the vane 5 to move from one end to the other and back. One of advantages in positioning the first pump 70 a and the second pump 70 b in series, compared with a configuration in which the second pump 70 b draws oil directly from the oil pan 75 is that it is possible to reduce the drawing power of the second pump 70 b. With a reduced drawing power requirement for the second pump 70 b, it is possible to employ a smaller-sized electric pump as the second pump 70 b, thereby enabling to reduce the size, and weight, of the entire structure of the variable valve timing control unit 100. As another advantage of arranging the first pump 70 a and the second pump 70 b in series, the total length of piping can be reduced, thereby making it possible to reduce an efficiency loss due to frictional resistance of the flowing oil.

It is preferable to provide a bypass passage 73 for bypassing the second pump 70 b. Therefore, if the second pump 70 b becomes inoperative and an oil passage in the second pump 70 b is closed, the oil drawn by the first pump 70 a can be fed to the bypass passage 73 thus assuring secure oil supply to the variable valve timing control unit 100 while the engine E is running.

THIRD EMBODIMENT

As is illustrated in FIG. 12, a variable valve timing control apparatus 1 according to a third embodiment of the present invention is provided with an engine stop delaying module (an engine stop delaying means) 96, while other configuration thereof is substantially identical to the first embodiment. Further, FIG. 12 illustrates an engine-controlling module (an engine controlling means) 110 which is not shown in other figures. However, this engine-controlling module 110 is provided in the apparatus 1 according to the other embodiments.

According to this third embodiment, in accordance with predetermined conditions described later, the engine stop control is performed in such a manner that the predetermined intermediate lock is carried out after delaying the halting of the operation of the first pump 70 a. The operations relevant to this engine stop control are illustrated in the flowchart in FIG. 14. In this flowchart, the module (means), which carries out respective step, is indicated on the left side thereof, and operating conditions of the first pump 70 a and the second pump 70 b, which are characteristic of the present invention, are indicated on the right side thereof.

Here, when the engine stop predicting module 93 predicts the stop of the engine E, i.e., when the ignition key 9 e is turned to the off position, the engine stop delaying module 96 outputs an engine stop delay signal for delaying an engine stop for a predetermined time (e.g., one or two seconds) from the time an engine stop is predicted. An elapsed time after outputting an engine stop delay signal, and an elapsed time after actually stopping the engine E are used as bases for decisions made in the algorism.

This engine stop control is implemented by the flowchart illustrated in FIG. 14.

Step 131

The engine stop-predicting module 93 determines whether the ignition key 9 e is turned to the off position. If it is not and a negative answer no is obtained at step 131, the program proceeds to step 130 so as to perform the above-described relative rotational phase control. Since the engine E is still running, the first pump 70 a continues to operate. Further, the spool of the control valve 76 is located at one of the positions W3, W4 and W5.

Steps 132 and 133

If the ignition key 9 e is turned to the off position resulting in “Yes” in step 131, the program proceeds to step 132, and the engine stop delaying means module 96 outputs an engine stop delay signal to the engine controlling module 110. At or about the same time, in step 133, the second pump 70 b is started on the basis of a control command from the engine stop-controlling module 94. Here, because an engine stop is delayed, the operation of the first pump 70 a is continued for a predetermined period of time, the first pump 70 a acts to assist the operation of the second pump 70 b whose operation was just started. Therefore, it is possible to reduce a load applied to the second pump 70 b when the engine E is started. Therefore, a smaller electric pump may be used, which leads to a smaller and lighter apparatus 1.

Steps 134 and 135

At or about the same time, the control valve 76 receives a control command to shift the spool of the control valve 76 from one of the positions W3, W4 and W5 to the position W2. That is, in step 134, the oil pressure in the lock oil chamber 62 is drained in order to operate the lock mechanism 6. After this drain operation in step 134, a sweep control is implemented in step 135.

Step 136

Following step 135, at step 136, the ECU 9 determines whether the relative rotational phase has reached the intermediate phase at which the locked condition is established. If it has and a positive answer yes is obtained in step 136, the program proceeds to step 137, and the engine E is stopped at step 138. On the other hand, if the phase has not reached the intermediate phase and a negative answer no is obtained in step 136, the program proceeds to step 139.

Step 139

This decision step 139 is to set a limit to the maximum period of time for performing the engine stop control. The ECU 9 determines, on the basis of an elapsed time after the ignition key 9 a is turned to the off position, whether the sweep control in step 135 should be repeated or the engine stop control in step 149 should be performed. When the predetermined period of time was determined to have passed in step 139, the program proceeds to step 140 to stop the engine E. On the other hand, if the predetermined period of time has not passed, the program returns to step 135 so as to further perform the sweep control.

Steps 141 and 142

After halting the engine E in step 140, the sweep control is implemented in step 141. Because the engine E has halted, this sweep control is performed only by the second pump 70 b. In step 142, the ECU 9 determines whether the relative rotational phase has reached the intermediate phase at which the locked condition is established. If it has and a positive answer yes is obtained in step 142, the program proceeds to step 143. On the other hand, if the phase has not reached the intermediate phase and a negative answer no is obtained at step 142, the program proceeds to step 144.

Step 144

Here, the ECU 9 determines whether a predetermined period of time has passed after halting the engine E at step 140. When the predetermined period of time is determined to have passed, the program proceeds to step 143 to terminate the engine stop control. When the predetermined period of time is determined to have not passed, the program returns to step 142, wherein the sweep control is further implemented by the second pump 70 b.

As described above, irrespective of implementing the engine start-up control, in the variable valve timing control apparatus 1 with the first pump 70 a and the second pump 70 b, for example, it is preferable to include the engine stop predicting module 93 for predicting an engine stop, and an engine stop controlling module 94, which, when the engine stop predicting module 93 predicts an engine stop, implements an engine stop control by operating the second pump 70 b. These arrangements make it possible to obtain an oil pressure reliably when the engine E is stopped, and further to complete preparations for an engine startup while the engine E is not running.

FOURTH EMBODIMENT

As is illustrated in FIG. 13, the variable valve timing control apparatus according to the fourth embodiment of the present invention is provided with an engine stop operation predicting module (an engine stop operation predicting means) 97, while other configuration thereof is substantially identical to the first embodiment. FIG. 13 illustrates a driven system 160 which is not illustrated in other figures. However, this driven system 160 is provided in the apparatus 1 according to the other embodiments.

Here, an engine stop operation predicting control is performed by means of the engine stop operation-predicting module 97. The engine stop operation predicting control is a one implemented based on a predetermined predicted condition such as an engine stop operation (e.g. a turning of the ignition key 9 e to its off position). This predetermined condition is described later.

The engine stop operation-predicting module 97 is incorporated in the ECU 9 illustrated in FIG. 13, for example, and can be hardware or software or a combination of both. This engine stop operation-predicting module 97 outputs, in response to prediction of the stop operation of the engine E, a command to the engine stop-controlling module 94 such that a standby operation of the second pump 70 b is performed with a predetermined output (e.g., 20 to 30% output). With this arrangement, because the second pump 70 b is preliminarily operated before an actual engine stop operation, it allows the second pump 70 b to make sufficient output immediately after the engine stop operation. Therefore, the arrangement makes it possible to smoothly and rapidly supply oil to the variable valve timing control unit 100 by the second pump 70 b immediately after the engine stop. This engine stop operation predicting control is described below with reference to the flowchart illustrated in FIG. 15.

Steps 151, 152, 153

In step 151, the engine stop operation-predicting module 97 determines whether engine stop operation predicting conditions are satisfied. The engine stop operation predicting conditions can be determined on the basis of one or the other of the rotational speed of the engine E, and a running condition of the driven system 160 to which the driving force of the engine E is transmitted. For example, the engine rotational speed is considered to satisfy the engine stop operation predicting condition if it is at or approximately at an idling speed (for example, the idling rotational speed +500 rpm or less). Further, for example, the running condition of the driven system 160 to which driving force of the engine E is transmitted is determined on the basis of a position of a shift lever or a speed value indicated by a speedometer. Specifically, when the transmission is in the park position, the engine stop operation predicting condition is satisfied if the vehicle speed outputted, for example, by a vehicle speed sensor is substantially zero. Since the engine stop operation is predicted on the basis of at least one piece of information, it is possible to supply oil more reliably to the variable valve timing control apparatus 1 immediately after an engine stop. When the engine stop operation predicting module 97 determines that the engine stop operation predicting condition is satisfied, in response to a control command from the engine stop controlling module 94, the standby operation of the second pump 70 b is started (step 152). During this time, the relative rotational phase control is implemented (step 153) as long as the engine E is running. If the engine stop operation predicting condition is not satisfied, this routine is repeated.

Step 154

Here, the engine stop predicting module 93 determines whether the ignition key 9 e was turned to its off position. When the ignition key 9 e is determine to have been turned to the off position, the program proceeds to step 157, wherein the engine stop control described above is implemented. That is, steps 73-78 in FIG. 7, steps 83-87 in FIG. 8, and steps 134-143 in FIG. 14 are carried out. On the other hand, if the ignition key 9 e is determined to have not been turned to the off position, the program proceeds to step 155.

Steps 155 and 156

In step 155, the engine stop operation predicting module 97 determines whether the engine stop operation predicting condition is not satisfied any more. For example, when the position of the shift lever is shifted from the parking position to a drive position (D), when the engine rotational speed increases to well beyond the idling speed, or when the speedometer indicates a non-zero speed, the ECU 9 determines that the engine stop operation predicting condition is not satisfied any more. In this case, the program proceeds to step 156, wherein the engine stop operation predicting control is terminated.

As described above, the arrangement according to the fourth embodiment of the present invention makes it possible to preliminarily operate the second pump 70 b prior to turning the ignition key 9 e to the off position. Therefore, the second pump 70 b is brought to its full capacity immediately after the first pump 70 a is stopped in response to the engine stop, thereby allowing smooth and stable supply of oil to the variable valve controlling unit 100 immediately after an engine stop.

FURTHER EMBODIMENT

According to the above described embodiments, the second pump 70 b is employed as an oil pressure source for the variable valve timing control unit 100. Alternatively or in addition to any of the foregoing embodiments, this second pump can be used to pump lubrication oil to the bearing portion of a supercharger of a vehicle. With this arrangement, because an oil pump can be operated even after an engine stop, by supplying oil to a bearing portion of a supercharger that still remains at a high temperature, the bearing seizure can be prevented. Further, it is possible to effectively prevent engine oil from being degraded, which on occasions occurs due to seizures of mechanical parts. As described above, because oil can be circulated only to a portion of a supercharger after an engine stop, a turbo timer, which circulates oil by running the engine, is not needed. Further, because the engine does not have to be running, the arrangement helps improve fuel efficiency.

A system for detecting an intake air temperature is not described above. This intake air temperature can be detected by providing a temperature-detecting unit at an air intake portion. The second start-up phase, which is needed for the engine start-up control, can be determined on the basis of this temperature.

The principles, the preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention, which is intended to be protected, is not to be construed as limited to the particular embodiment disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents that fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby. 

1. A variable valve timing control apparatus comprising: a drive-side rotational member rotatable in synchronization with a crankshaft; a driven-side rotational member positioned coaxially with the drive-side rotational member and being rotatable integrally with a camshaft; a fluid pressure chamber defined between the drive-side rotational member and the driven-side rotational member; a vane dividing the fluid pressure chamber into an advanced angle chamber and a retarded angle chamber; a relative rotational phase adjusting mechanism changing a position of the vane relative to the fluid pressure chamber by supplying hydraulic fluid to or draining hydraulic fluid from at least one of the advanced angle chamber and the retarded angle chamber the relative rotational phase adjusting mechanism adjusting a relative rotational phase between the drive-side rotational member and the driven-side rotational member between the most advanced angle phase, in which a volume of the advanced angle chamber reaches maximum, and the most retarded angle phase, in which a volume of the retarded angle chamber reaches maximum; a lock mechanism locking the relative rotational phase at an intermediate phase between the most advanced angle phase and the most retarded angle phase; a first pump operated by a driving force of an engine; an electrically driven second pump wherein the hydraulic fluid is supplied from at least one of the first pump and the second pump and the second pump is operated when the engine is stopped; an engine start-up predicting means for predicting a start-up of the engine; and an engine start-up controlling means for implementing an engine start-up control by operating the second pump when an engine start-up is predicted by the engine start-up predicting means.
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled)
 6. A variable valve timing control apparatus according to claim 1, wherein the engine start-up control implemented by the engine start-up controlling means is an engine start-up lock control wherein the lock mechanism is operated to lock the relative rotational phase at a first start-up phase that is suitable for an engine start-up.
 7. A variable valve timing control apparatus according to claim 1, wherein the engine start-up control implemented by the engine start-up controlling means is an engine start-up phase control which changes the relative rotational phase to a second start-up phase that is different from the first start-up phase at which the relative rotational phase is locked by the lock mechanism.
 8. A variable valve timing control apparatus according to claim 7, wherein the second start-up phase is determined based upon at least one of an engine oil temperature, a water temperature, and intake air temperature, and an outside air temperature.
 9. A variable valve timing control apparatus according to claim 7, wherein, after stopping the engine and prior to starting the engine, the lock mechanism is operated so as to implement an engine lock control whereby the relative rotational phase is locked at the first start-up phase suitable for an engine start-up.
 10. A variable valve timing control apparatus comprising: a drive-side rotational member rotatable in synchronization with a crankshaft; a driven-side rotational member positioned coaxially with the drive-side rotational member and being rotatable integrally with a camshaft; a fluid pressure chamber defined between the drive-side rotational member and the driven-side rotational member; a vane dividing the fluid pressure chamber into an advanced angle chamber and a retarded angle chamber; a relative rotational phase adjusting mechanism changing a position of the vane relative to the fluid pressure chamber by supplying hydraulic fluid to or draining hydraulic fluid from at least one of the advanced angle chamber and the retarded angle chamber, the relative rotational phase adjusting mechanism adjusting a relative rotational phase between the drive-side rotational member and the driven-side rotational member between the most advanced angle phase, in which a volume of the advanced angle chamber reaches maximum, and the most retarded angle phase, in which a volume of the retarded angle chamber reaches maximum; a lock mechanism locking the relative rotational phase at an intermediate phase between the most advanced angle phase and the most retarded angle phase; a first pump operated by a driving force of an engine; an electrically driven second pump; wherein the hydraulic fluid is supplied from at least one of the first pump and the second pump, and the second pump is capable of operating when the engine is stopped; an engine stop predicting means for predicting an engine stop; an engine stop controlling means for implementing an engine stop control by operating the second pump when the engine stop predicting means predicts an engine stop; and wherein the engine stop control implemented by the engine stop controlling means is an engine stop lock control wherein a sweep operation, which adjusts the relative rotational phase to the most advanced angle phase or the most retarded angle phase, is performed, and the lock mechanism is operated to lock the relative rotational phase at the first start-up phase which is suitable for an engine start-up.
 11. (canceled)
 12. A variable valve timing control apparatus according to claim 10, further comprising: an engine stop delaying means for outputting, to an engine controlling means for controlling the engine, an engine stop delay signal for delaying the engine stop for a predetermined time when the engine stop predicting means predicts an engine stop.
 13. A variable valve timing control apparatus according to claim 10, further comprising: an engine stop operation predicting means for predicting a stop operation of the engine, wherein, when the engine stop operation predicting means predicts the stop operation of the engine, the engine stop controlling means allows the second pump to perform a standby operation at a predetermined output.
 14. A variable valve timing control apparatus according to claim 13, wherein the engine stop operation predicting means predicts the stop operation of the engine based upon at least one of a rotational speed of the engine and a running condition of a driven system to which a driving force of the engine is transmitted.
 15. A variable valve timing control apparatus according to claim 1, wherein the first pump and the second pump are arranged in parallel with each other.
 16. A variable valve timing control apparatus according to claim 1, wherein the second pump is arranged in series with and on the downstream side of the first pump, and wherein a oil reservoir is positioned between the first pump and the second pump.
 17. A variable valve timing control apparatus according to claim 16 further comprising a bypass passage that allows hydraulic fluid to bypass the second pump.
 18. A variable valve timing control apparatus according to claim 10, wherein the first pump and the second pump are arranged in parallel with each other.
 19. A variable valve timing control apparatus according to claim 10, wherein the second pump is arranged in series with and on the downstream side of the first pump, and wherein a oil reservoir is positioned between the first pump and the second pump.
 20. A variable valve timing control apparatus according to claim 19 further comprising a bypass passage that allows hydraulic fluid to bypass the second pump. 